> 5% per minute is not extremely fast.

5% of nameplate capacity.

> You'd think it means "changing the power output from moment to moment to match electricity demand" but for nuclear plants it means "changing from one pre-planned constant level to another pre-planned constant level, up to four times per day"

Which is clearly invalidated by the very source I provided, and which you then somehow quote back at me.

> "the number of such very fast power variations is limited, and they are mainly reserved for emergency situations." per your source.

Imagine if you didn't omit the full quote/context:

--- start quote ---

Also, AES-2006 is capable of fast power modulations with ramps of up to 5% Pr per second (in the interval of ±10% Pr), or power drops of 20% Pr per minute in the interval of 50-100% of the rated power. However, the number of such very fast power variations is limited, and they are mainly reserved for emergency situations.

--- end quote ---

Oh look. What's limited is an actual emergency ramp up of 5% per second or power drops of 20% per minute.

Which is literally an emergency that is not needed in a power grid.